cobra r 5.4....low boost with vortech v7 ysi on

[Bill Anderson]

Hello,

I just installed a Vortech v7 ysi on a 2000 cobra r 5.4.

8 rib 2.7" vortech renegade pulley

8 rib 6.5" innovator's west balancer

stock 8 rib tensioner

dayco gold micro v belt

paxton air to air charge cooler.

mondo bypass valve

pull through sct ba3000 maf with 4" piping from filter to blower inlet

VP MS-109 (just switched to Shell URT advanced)

last couple of pulls on dyno, car starts making approx 11.6 lbs of boost at around 4500, and stays there all the way to 7k.

car made 703 @ 6800 with 11.6 lbs.

My problem is that I expected around 18-20lbs with that pulley setup. I checked for boost leaks and verified that the bypass valve was not leaking.

there was a little belt dust at 1st, but no more.

I am pretty much out of ideas and wanted some input from you folks here:

Do I need to goto an overdrive balancer?

switch out the blower pulley to a reichard racing slotted version?

different tensioner....?

I hate swapping parts when I can't prove that is where the problem is, for example, I can't prove the belt is slipping, but I am at a loss as to why I am making so little boost.

my target hp was to be around 800 or so, I am sure if I can squeeze another 5-6 lbs, I will see it...any ideas guys?

I know this question has come up numerous times on the internet with a thousand different remedies....sure could use some sound direction here...

thanks in advance for the help

 

[98 Saleen Cobra]

Yup you have belt slip buddy.. I would switch to a 10-15% O/D crank pulley and get a blower pulley for the same blower RPM as what it is at now at shift point.. Also your stock tensioner probably isn't holding shit lol.. Get a ThumpRRR tension and the belt slip issues will be solved But I that is exactly what you are having.. That is exactly what belt slip looks like on a boost gauge and the dust just proves it.. Trust.

 

[AluminatorSnake]

Yup sounds like belt slip, the boost should be climing instead of holding around 11psi. Get a good tensioner like stated above, then crank pulley if need be, and possibly even try the carbinite pulley coating. Seems like guys are just picking up 1-2psi just by having their pulley coated.

 

[dtheo]

damn, would love to see street video of this beast!

 

[97snakebite]

Yup sounds like belt slip, the boost should be climing instead of holding around 11psi. Get a good tensioner like stated above, then crank pulley if need be, and possibly even try the carbinite pulley coating. Seems like guys are just picking up 1-2psi just by having their pulley coated.

can u give a lil more info on the pulley coating?? coating with what?

 

[01yellercobra]

can u give a lil more info on the pulley coating?? coating with what?

Applications

I had it done to a pulley, but sold it before I used it.

 

[Bill Anderson]

Thanks guys...

the R uses a non a/c 5.4 / v10 97-04 f150-250 tensioner....picked up a spare and sent it up to thump racing, it is clocked different than a standard modular tensioner, but he thinks he can make me one up...The vortech renegade pulleys are supposed to have some type of coating already applied.

I have to remove the blower to get to the tensioner and I already have a 2.70 reichard racing pulley, seems like folks either love um or hate um

any comments on the reichard pullies?

 

[Bill Anderson]

I have some pics of the project in the cobra r section, if you are interested in seeing the install, you can find it if you search for posts under my name...thanks again for the help.

alot of fabrication had to be done to do the install, but the car is awesome even with just 11 lbs

 

[encasedmetal]

just a simple matter of belt contact surface area. 2.7" blower pulley and 6.5" crank pulley do not make for much contact. I suggest both a larger blower pulley and a larger crank pulley. I run a 4" blower pulley and 8" outer crank pulley with my F1a and it makes 22.5psi

 

[jpicc]

The 2.70 compressor pulley is where the root of your problem is. There is not enough surface area on that diameter pulley for grip. I have a 2.95" with no issues, I have tried the 2.70 and had slip issues with it on my YSI set-up.

 

[b00sted4v]

just sell it to me :-D

 

[99cobra09]

Get a 3.00" blower pulley with a 15% overdrive crank. The stock tensioner will do with this set up but a thupr rr will be better. carbinite coating pulleys are the best for these centri blowers.

 

[CBelleperche]

I have a 10% OD dampner with a 2.8 high traction Vortech pulley on my Ysi and I make 18lbs at 6800 rpm. Most likely slip. On the dyno graph did it look like a wave by any chance?

 

[Bill Anderson]

I have a 10% OD dampner with a 2.8 high traction Vortech pulley on my Ysi and I make 18lbs at 6800 rpm. Most likely slip. On the dyno graph did it look like a wave by any chance?

Not really, boost climbed smoothly to 11.6 lbs to 4500, then just seemed to level off all the way to 7k....At 1st it looked as though the mondo bypass was acting like a regulator and bleeding off boost, so I took it off and bench tested it with compressed air and it held tight past 20 lbs...put check valves in all of the vacuum hoses and pcv and moved the IAC connection from the cold air pipe to the discharge side of the compressor.. ...no change

At 1st there was some notable belt dust, but that subsided after a couple of pulls. I did mark the belt and pulley, made a pull, and the marks did move out of alignment, but I assume serpentine belts are supposed to have "Some" slippage...

I Purchased a couple of different diameter innovator's west balancers (10% and a 15% od) some smaller alternator pulleys (the R came with a 4" and is very close to the 2.7 blower pulley). to go to a larger pulley on the blower, I have to goto a smaller alt pulley for clearance.

picked up an assortment of vortech pulleys as well as a reichard racing 2.7 and also have a new tensioner coming from thump racing.

I am going to try the reichard 2.7 with the thump racing tensioner 1st, just because once I start going to a larger balancer, I will have to grind the timing cover a bit, and a larger blower pulley will require changing the alt pulley as well as re-designing the water crossover (yep, it is that close).



All of the ideas given so far are sound ones...getting the most belt contact on the pulleys is the key...it is just a matter of working with it until the the right combo is found.


Thanks for all of the good suggestions, hopefully one of the combinations will get the boost up to where it needs to be.

 

[mtrsprt]

If your boost levels off and flatlines, you either are bleeding pressure from your bypass/discharge piping somewhere, or a valve is hanging open slightly.

Even with a 2.7, you should make it higher than 4500rpm before it slips. When the belt slips bad enough, usually you can see it happen on the gauge.

Check your discharge valve, and all your piping etc first. If you feel it's all sealed and tight, then like others said. Move on to a 7.25-7.50"(10-15%) crank damper, and 2.85-3.00 compressor pulley.

Also, this isn't the first time people have had the Vortech Mondo valve bleed off pressure unexpectedly.